It is often desirable to perform sulfuration (generally called "presulfuration or sulfurizing") of metals that fall within the composition of certain refining catalysts and/or hydrocarbon hydroconversion catalysts, either when these catalysts are new or at the end of the regeneration of these catalysts before they are reused.
Presulfurizing fresh or regenerated catalysts is thus desirable in order to use these catalysts in refining reactions, for example, the reactions of hydrotreating or hydrodesulfurizing or hydrocracking of various petroleum fractions whose sulfur content has to be reduced or whose other characteristics are to be improved before use.
Thus, in the prior art, the catalyst, fresh or regenerated, before being used, was generally subjected to sulfuration (presulfuration) that was carried out in a hydrodesulfuration reactor. This sulfuration makes it possible to include in the catalyst, for example, about 50 to 110% of the stoichiometric amounts of sulfur that are calculated based on the following chemical formulas Co.sub.9 S.sub.8, MoS.sub.2, WS.sub.2 and Ni.sub.3 S.sub.2.
The regeneration of catalysts is now being done more and more by someone specialized in catalyst regeneration, sometimes in a different site from the industrial unit. It seems reasonable, however, to consider returning to the refiner a product that is ready for use; this is done in order to make possible the efficient process of the applicant's European patent EP-B,130850 (or U.S. Pat. No. 4,530,917), in which a sulfurated compound is incorporated into the catalytic compound and said compound causes the sulfuration or presulfuration of the catalyst when, later, the catalyst is brought into contact with hydrogen in the reaction zone (zone for treating the batch) or in the immediate vicinity of the reaction zone.
More specifically, in the applicant's European Patent No. EP-B-130850 or U.S. Pat. No. 4,530,917 (process called SULFICAT), the process of sulfuration of the catalyst is therefore characterized by a so-called preliminary stage for incorporation of a sulfur-containing compound of a special nature into the catalytic compound.
The preliminary stage of introducing a sulfur-containing compound, which is arbitrarily called "off-site" or "ex-situ" pretreatment, whether it is carried out close to the site of the industrial unit or more or less geographically distant from the industrial unit (where the catalyst has been regenerated or where it was produced, for example), is no longer performed, in any case, in the immediate vicinity of the reactor ("in situ" is written arbitrarily), i.e., at the reactor heads or in zones that are more or less in direct communication with these reactors, thus requiring operations to be performed under operating conditions (of temperature, pressure or the like) that are imposed at least in part by the operating conditions of the reactors themselves or attachments to these reactors (preliminary hydrogenation zone of the catalyst, for example).
In short, the applicant's European Patent EP-8-130850 relates to a process (which is thus called SULFICAT that makes it possible, (when the catalyst will be subjected from start-up, preferably on site ("in situ"), to the standard activation reaction in the presence of hydrogen, above 100.degree. C., and then thanks to the presence of hydrogen on the site), to undertake the sulfuration at the required rate, stoichiometric or non-stoichiometric, of the active metal or active metals that are part of the composition of the catalyst. The process consists in incorporating at least one organic polysulfide into the pores of the fresh or regenerated catalyst in the absence of hydrogen.
The sulfuration of the catalyst can thus be done as follows: in a first stage, which is performed "ex-situ," with no hydrogen, the catalyst is treated by means of the sulfurizing agent to incorporate this agent partially or totally into the pores of the catalyst, with said sulfurizing agent being used in solution in a solvent; in a second stage, which is performed "in situ" and preferably at temperatures above 150.degree. C., an activation stage of the catalyst that is carried out with hydrogen is initiated, with the required amount of sulfur being fixed thanks to the presence of hydrogen on the metal or metals that are part of the composition of said catalyst.
The technique that is described above has been improved in Patent EP-B-181,254 or U.S. Pat. No. 4,719,195. The object of these two patents is to carry out the presulfuration of the catalysts "ex situ" by incorporating all of the sulfur required and only the amount of sulfur required by the user. The catalysts are therefore supplied to the refinery or any other unit preconditioned for sulfuration.
The presulfurizing agent therein was an organic polysulfide. Di-tert-dodecylpolysulfide (TPS 32 of ELF) can be cited as a preferred example of polysulfide. Di-tert-nonylpolysulfide (TPS 37 of ELF) can also be cited. The sulfurizing agent is used diluted in a suitable solvent. The solvent selected can thus be one of the following solvents, which are used alone or mixed together:
a light gasoline that boils at, for example, between about 60 and 95.degree. C., PA1 a hexane type gasoline that boils at between about 65 and 68.degree. C., PA1 an F-type gasoline that boils at between about 100 and 160.degree. C., PA1 a "white spirit" type gasoline that boils at between about 150 and 250.degree. C., PA1 or any fraction that may or may not contain hydrocarbon, equivalent to the above gasolines. PA1 as alcohols, hexanols, heptanols, octanols, nonanols, decanols, dodecanols, and higher alcohols, linear alcohols or branched alcohols, diols or polyols and carbohydrates. As examples of diols or polyols, let us cite in particular: PA1 as mercaptans (or thiol) and polymercaptans, the compounds that correspond to said alcohols where the OH group is replaced by the SH group, PA1 as aldehydes, the compounds that correspond to said alcohols where a terminal CH.sub.2 OH group is replaced by a CHO group, PA1 as acids, the compounds that correspond to said alcohols where a terminal CH.sub.2 OH group is replaced by a COOH group. Fatty acids can also be used. PA1 as esters, the compounds that correspond to said alcohols where a terminal CH.sub.2 OH group is replaced by a COOR group, with R being a radical that contains one or more carbon atoms (methyl, ethyl, etc. . . ); fatty acid esters can also be used. PA1 as ketones, hexanones can be used with dodecanones or ketones of higher molecular weight. PA1 as ethers, any compound that results from the dehydrating combination of two said alcohols or one said alcohol and another lighter alcohol such as methanol or ethanol (illustrative example: a methyl dodecyl ether) or two other lighter alcohols, such as methyl tert-butyl ether (MTBE) or methyl tert-amyl ether (TAME), and even cyclic ethers such as tetrahydrofuran or dioxane.
The SULFICAT process that is described above was improved after it was discovered that the qualities of the methods described in Patents EP-B-130,850 (U.S. Pat. No. 4,530,917) and EP-B-181254 (U.S. Pat. No. 4,719,195) of the applicant were further improved if the organic polysulfide was not used alone, but mixed in critical amounts with elemental sulfur.
This improved technique of the applicant is described in EP-B-448435 or U.S. Pat. No. 5,139,983. Elemental sulfur is used in the form of, for example, molten sulfur, sulfur powder, or sulfur flour, according to any suitable method, for example, the one described in the applicant's patent EP-B-153233.
The preceding processes were the object of another type of improvement by the applicant, which is described in EP-B-466 568 (U.S. Pat. No. 5,153,163) called "SURECAT" and relates to the pre-reduction of the catalyst accompanied by sulfurizing passivation.
In another process of the applicant, described in EP-B-564 317, the presulfuration of the catalyst is carried out either in the presence of at least one organic polysulfide, or in the presence of elemental sulfur, or by means of at least one organic polysulfide and elemental sulfur at the same time. Preferably, a mixture of at least one organic polysulfide and elemental sulfur is used. The solvent used is generally and preferably a white spirit or an equivalent solvent. An olefinic compound, particularly such as rapeseed oil, is also used.
It should be noted that other patents, and particularly U.S. Pat. No. 4,943,547 and U.S. Pat. No. 5,215,954, also relate to the presulfuration of catalysts by a method that makes it possible to incorporate elemental sulfur into the pores of the catalyst; but here the elemental sulfur penetrates the pores basically by melting or by sublimation.